1. Field of Invention
The present invention relates to an apparatus and method for controlling a urea injection amount of a vehicle that determines a urea injection amount according to a collection amount of soot that is collected at an SCR integral diesel particulate filter and an accumulation amount of ash.
2. Description of Related Art
In a vehicle, in a system in which an SCR catalyst and a diesel particulate filter (DPF) are separated, in a method of determining a urea injection amount, a necessary amount of NH3 is calculated according to a stoichiometric ratio (NH3/NOx), which is a ratio of NH3 and an amount of NOx that are exhausted from an engine.
As another method, a method of calculating a necessary amount of NH3 by subtracting a consumption amount of NH3 from a storage amount of NH3 on an SCR catalyst may be applied.
A system in which the SCR catalyst and the diesel particulate filter are separately formed determines a storage amount of NH3 by reflecting a temperature of the SCR catalyst, an exhaust flow velocity, a catalyst aging degree, and an HC adsorption amount.
In order to provide cost reduction, weight reduction, and efficient package of an aftertreatment device, an SCR integral diesel particulate filter that coats the inside of the diesel particulate filter with an SCR catalyst is applied.
In the SCR integral diesel particulate filter, because an SCR carrier and canning are removed, a weight is reduced, and thus fuel consumption is enhanced.
Because the SCR integral diesel particulate filter may be moved and mounted at the upstream side of an exhaust pipe, a NOx purification performance can be improved due to rise of an exhaust gas temperature.
However, in the SCR integral diesel particulate filter, as a collection amount of soot enlarges, a contact area of an exhaust gas and an SCR catalyst decreases and thus a storage amount of NH3 reduces.
As a travel distance of a vehicle enlarges, an accumulation amount of ash increases and thus an effective volume of the SCR integral diesel particulate filter reduces, thereby reducing a storage amount of NH3.
Therefore, when applying a general NH3 reaction rate model to the SCR integral diesel particulate filter, as a collection amount of soot and an accumulation amount of ash enlarge, control precision of a storage amount of NH3 is deteriorated and thus slip of NH3 may occur.
Exemplars of known methods are Korean Patent No. 10-0857346 (Sep. 1, 2008) and Korean Patent Laid-Open Publication No. 10-2012-0018999 (Mar. 6, 2012).
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.